Reading is both visual and linguistic. Visual perceptual stimuli (letters, words, and sentences) first activate cerebral cortical visual networks, then language networks. Reading should therefore be studied using an interdisciplinary approach that accounts for both visual and linguistic processes. [unreadable] [unreadable] Models of reading and its disorders have included developmental dyslexia and lesion studies. While such models have unquestionably advanced understanding of reading, they are nonetheless limited: the pathophysiologic basis of developmental dyslexia is not known, acquired alexia is often accompanied by other neurologic deficits, and lesions are rarely identical across subjects. [unreadable] [unreadable] Alzheimer's disease (AD) is another potentially informative but under-characterized model of abnormal reading. The pathophysiology is known, the progression of pathology is relatively consistent across subjects, and the disease consistently affects areas known to be involved in reading and language (particularly the supramarginal and angular gyri). There is a wealth of data on language changes in AD, and difficulty communicating (including reading written reminders and treatment instructions) exacerbates disease burden for patients and caregivers. Whether this differs from healthy aging (and if so, how) is not known. [unreadable] [unreadable] Our laboratory has extensive experience characterizing visual perceptual changes in AD, and we have shown that visual perceptual changes in AD are quantitatively different from normal aging. We now propose using refined psychophysical and linguistic methods to quantitatively evaluate the contribution of visual perceptual abnormalities to reading disorders in AD. We hypothesize that higher order deficits of visuoperceptual and linguistic function interact to create a spectrum of reading impairments in aging and Alzheimer's disease. Our approach integrates visual perception and linguistics, and we will test our hypothesis in a series of experiments to quantify the contributions of both visual and linguistic deficits to reading impairment. Our goal is to develop a new paradigm for understanding reading disorders by [unreadable] unifying the psychophysical and linguistic perspectives. This will lead to new methods for early detection of reading disorders in aging and AD, the diagnosis of specific impairments, and guiding new therapies. [unreadable] [unreadable] The applicant's mentors have extensive complementary expertise to guide the research project. The career development plan will facilitate the applicant's transition to an independently funded researcher by the end of the award period. [unreadable] [unreadable]